linux-kernel - [PATCH 4.14 17/75] PM / Domains: Fix genpd to deal with drivers returning 1 from ->prepare()

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Message-Id: <20171207130819.440764447@linuxfoundation.org>
Date:   Thu,  7 Dec 2017 14:07:39 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ulf Hansson <ulf.hansson@...aro.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.14 17/75] PM / Domains: Fix genpd to deal with drivers returning 1 from ->prepare()

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ulf Hansson <ulf.hansson@...aro.org>

[ Upstream commit 5241ab40f6e742f8a1631f8826faf6dc6412b3b5 ]

During system-wide PM, genpd relies on its PM callbacks to be invoked for
all its attached devices, as to deal with powering off/on the PM domain. In
other words, genpd is not compatible with the direct_complete path, if
executed by the PM core for any of its attached devices.

However, when genpd's ->prepare() callback invokes pm_generic_prepare(), it
does not take into account that it may return 1. Instead it treats that as
an error internally and expects the PM core to abort the prepare phase and
roll back. This leads to genpd not properly powering on/off the PM domain,
because its internal counters gets wrongly balanced.

To fix the behaviour, allow drivers to return 1 from their ->prepare()
callbacks, but let's return 0 from genpd's ->prepare() callback in such
case, as that prevents the PM core from running the direct_complete path
for the device.

Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/base/power/domain.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -921,7 +921,7 @@ static int pm_genpd_prepare(struct devic
 	genpd_unlock(genpd);

 	ret = pm_generic_prepare(dev);
-	if (ret) {
+	if (ret < 0) {
 		genpd_lock(genpd);

 		genpd->prepared_count--;
@@ -929,7 +929,8 @@ static int pm_genpd_prepare(struct devic
 		genpd_unlock(genpd);
 	}

-	return ret;
+	/* Never return 1, as genpd don't cope with the direct_complete path. */
+	return ret >= 0 ? 0 : ret;
 }

 /**